Grate with central outlet duct



May 28, 1957 H. STURM GRATE WITH CENTRAL OUTLET DUCT 7 Filed June 18, 1953 FIG. I

INVEIWUP United States Patent 2,793,627 GRATE WITH CENTRAL OUTLET DUCT Hermann Sturm, Bad Cannstatt, Germany Application June 18, 1953, Serial No. 362,441

Claims priority, application Germany November 4, 1952 2 Claims. (Cl. 122--371) This invention relates to an annular grate in which the fuel is moved towards the centre of the grate where the residues of the combustion reach into a central outlet duct. In this case, it is not possible to avoid that parts of the fuel which have not yet been burned will pass into the outlet duct. The residues of combustion which have been discharged have still a high temperature. Thus, an amount of heat is lost. A further disadvantage lies in that, owing to the caking of the slag to the walls of the outlet duct, the latter is more or less stopped, and this causes disturbances in operation.

These disadvantages are avoided according to the invention by that the part of the outlet duct following immediately the grate is constituted by a coiled tube which is connected to the circulation of the boiler.

According to the invention, the pitch of, and the distance between, the turns of the coiled tube are so chosen that the steam bubbles in the coiled tube rise upwards and air of combustion between the turns can flow into the outlet duct formed by the coiled tube. In this way, steam cushions which disturb the Water circulation are avoided.

Further, according to the invention, there is provided at the lower end of the coiled tube a slag breaking cylinder acting as a discharge device, which cooperates with a tiltable and adjustable grate for aftercombustion. In this way, the amount that is discharged and the aftercombustion can be regulated within wide limits. Sintering of the slag residues is avoided by the wide adaptation of the mechanical discharge device and by the control of the after-combustion connected therewith.

The accompanying drawings illustrate the invention by Way of example, the representation being limited to the parts required for the understanding thereof.

Figure 1 shows mainly diagrammatically a central section of the annular grate; and

Figure 2 is a sectional plan view of Figure 1 along the line II-II, the grate rings being left out.

The annular grate, shown by way of example as a revolving grate, comprises the grate rings a, b, c which are disposed one above the other in a step-like manner and eccentrically with respect to each other. Owing to the eccentric mounting of the grate rings, when the same are rotated the fuel is shifted towards the centre of the grate. To the inner free annular space of the lowermost grate ring a there is connected, downwardly directed, the outlet duct, the wall of which is constituted by the coiled z 7 93 ,6'27 Fatented May 28, 1957 tube d. A casing member l surrounds at least a part of the tube d and is spaced therefrom with the lower end of the casing member being open to permit the discharge of the residue. The latter is connected at its ends to the circulation of the boiler. The free outlet space constituted by the coiled tube 01 is covered below by the after-combustion grate f tiltable around the pivot e, to the front edge of which a breaking cylinder g runs parallel. The position of inclination of the tiltable grate f and therewith the co-operation with the breaking cylinder g can be adjusted to the conditions of operation. In this way, the comminution, the conveying and the action of the after-combustion grate are influenced at the same time. The pitch of the turns of the coiled tube d and the distance of the windings from one another are so chosen that the air of combustion which flows in through air inlet pipes h can reach in suflicient quantity into the outlet space constituted by the coiled tube. The coiled tube a thus acts at the same time as an auxiliary combustion chamber for the after-combustion of the material that is being discharged. The tiltable grate 1 may also be turned downwards as is indicated in dotted lines in Figure 1, thereby completely opening the outlet duct.

I claim:

1. In a fuel combustion apparatus, the combination of an annular grate having a free central discharge opening with an outlet duct arranged immediately below and communicating with said discharge opening to receive the fuel residues from the annular grate, said outlet duct comprising a coiled water circulating tube having a water inlet at one end and a water outlet at the other end adapted to be connected to the water space of a boiler and said coil comprising a plurality of superposed convolutions in spaced relationship to one another, a casing member surrounding and spaced from at least a part of said convolutions and provided with an open end for the discharge of the fuel residues, air conduit means in communication with said casing member to supply air to pass from said easing into the outlet duct between the convolutions, and means including an adjustable aftercombustion grate arranged below the outlet duct for retaining the fuel residues in the outlet duct until the combustible constituents of the fuel residues therein have been completely burnt by air passing into the outlet duct between the convolutions and through the bottom of the outlet duct.

2. A fuel combustion apparatus as defined in claim 1 wherein a slag-breaking cylinder is positioned below said outlet duct and said after-combustion grate is provided with one edge thereof parallel to an adjacent the slagbreaking cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 1,739,135 Foresman Dec. 10, 1929 2,183,386 Yeager Dec. 12, 1939 2,211,269 James et al. Aug. 13, 1940 FOREIGN PATENTS 158,471 Switzerland Jan. 16, 1933 

